<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>省略</title>
</head>
<body>
    <script>
        /*function add(n){
            return n+5;
        }

        function show(n,fn){
            alert(fn(n));
        }

        show(5,add);*/
        show(5,n=>n+5);
    </script>
</body>
</html>